Question

Rust forms when iron metal reacts with oxygen gas. Which chemical reaction best

supports the law of conservation of mass?
A. Fe + O2 --> Fe2O3
B. 2Fe + O2 --> 2Fe2O3
C. 3Fe + 202 --> Fe2O3
D. 4Fe + 302 --> 2Fe2O3

Answer 1

D. 4Fe + 302 --> 2Fe2O3

Step-by-step explanation:

The equation that bests supports the law of conservation of mass is the choice D;

4Fe + 3O₂ → 2Fe₂O₃

Based on the law of conservation of mass, the number of atoms on both sides of the expression must be the same. Only the fourth choice proves this law;

4Fe + 3O₂ → 2Fe₂O₃

Number of atoms

Elements Left hand side Right hand side

Fe 4 4

O 6 6

We can see that both side of the expression have the same number of atoms and the equation is balanced.